Force invariant touch sensitive actuator

ABSTRACT

A load control device for controlling an amount of power delivered to an electrical load from an AC power source, the load control device comprising a semiconductor switch operable to be coupled in series electrical connection between the source and the load, the semiconductor switch having a control input for controlling the semiconductor switch between a non-conductive state and a conductive state; a controller operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between the non-conductive state and the conductive state; a touch sensitive front surface; a touch sensitive device responsive to a point actuation on the touch sensitive front surface, the point actuation characterized by a position and a force, the touch sensitive device comprising a resistive divider and an output operatively coupled to the controller for providing a control signal to the controller; and a capacitor coupled to the output of the touch sensitive device for stabilizing the control signal; wherein the capacitor is operable to charge and discharge through the resistive divider of the touch sensitive device, such that the control signal is representative of the position of the point actuation.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 11/471,914,filed Jun. 20, 2006 entitled FORCE INVARIANT TOUCH SENSITIVE ACTUATOR.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to load control devices for controllingthe amount of power delivered to an electrical load from a power source.More specifically, the present invention relates to a touch dimmerhaving a touch sensitive device.

2. Description of the Related Art

A conventional two-wire dimmer has two terminals: a “hot” terminal forconnection to an alternating-current (AC) power supply and a “dimmedhot” terminal for connection to a lighting load. Standard dimmers useone or more semiconductor switches, such as triacs or field effecttransistors (FETs), to control the current delivered to the lightingload and thus to control the intensity of the light. The semiconductorswitches are typically coupled between the hot and dimmed hot terminalsof the dimmer.

A conventional two-wire dimmer has two terminals: a “hot” terminal forconnection to an alternating-current (AC) power supply and a “dimmedhot” terminal for connection to a lighting load. Standard dimmers useone or more semiconductor switches, such as triacs or field effecttransistors (FETs), to control the current delivered to the lightingload and thus to control the intensity of the light. The semiconductorswitches are typically coupled between the hot and dimmed hot terminalsof the dimmer.

Smart wall-mounted dimmers include a user interface typically having aplurality of buttons for receiving inputs from a user and a plurality ofstatus indicators for providing feedback to the user. These smartdimmers typically include a microcontroller or other processing devicefor providing an advanced set of control features and feedback optionsto the end user. An example of a smart dimmer is described in greaterdetail in commonly assigned U.S. Pat. No. 5,248,919, issued on Sep. 28,1993, entitled LIGHTING CONTROL DEVICE, which is herein incorporated byreference in its entirety.

FIG. 1 is a front view of a user interface of a prior art smart dimmerswitch 10 for controlling the amount of power delivered from a source ofAC power to a lighting load. As shown, the dimmer switch 10 includes afaceplate 12, a bezel 14, an intensity selection actuator 16 forselecting a desired level of light intensity of a lighting load (notshown) controlled by the dimmer switch 10, and a control switch actuator18. Actuation of the upper portion 16A of the intensity selectionactuator 16 increases or raises the light intensity of the lightingload, while actuation of the lower portion 16B of the intensityselection actuator 16 decreases or lowers the light intensity. Theintensity selection actuator 16 may control a rocker switch, twoseparate push switches, or the like. The control switch actuator 18 maycontrol a push switch or any other suitable type of actuator andtypically provides tactile and auditory feedback to a user when pressed.

The smart dimmer 10 also includes an intensity level indicator in theform of a plurality of light sources 20, such as light-emitting diodes(LEDs). Light sources 20 may be arranged in an array (such as a lineararray as shown) representative of a range of light intensity levels ofthe lighting load being controlled. The intensity level of the lightingload may range from a minimum intensity level, which is preferably thelowest visible intensity, but which may be zero, or “full off,” to amaximum intensity level, which is typically “full on.” Light intensitylevel is typically expressed as a percentage of full intensity. Thus,when the lighting load is on, light intensity level may range from 1% to100%.

By illuminating a selected one of the light sources 20 depending uponlight intensity level, the position of the illuminated light sourcewithin the array provides a visual indication of the light intensityrelative to the range when the lamp or lamps being controlled are on.For example, seven LEDs are illustrated in FIG. 1. Illuminating theuppermost LED in the array will give an indication that the lightintensity level is at or near maximum. Illuminating the center LED willgive an indication that the light intensity level is at about themidpoint of the range. In addition, when the lamp or lamps beingcontrolled are off, all of the light sources 18 are illuminated at a lowlevel of illumination, while the LED representative of the presentintensity level in the on state is illuminated at a higher illuminationlevel. This enables the light source array to be more readily perceivedby the eye in a darkened environment, which assists a user in locatingthe switch in a dark room, for example, in order to actuate the switchto control the lights in the room, and provides sufficient contrastbetween the level-indicating LED and the remaining LEDs to enable a userto perceive the relative intensity level at a glance.

Touch dimmers (or “zip” dimmers) are known in the art. A touch dimmergenerally includes a touch-operated input device, such as a resistive ora capacitive touch pad. The touch-operated device responds to the forceand position of a point actuation on the surface of the device and inturn controls the semiconductor switches of the dimmer. An example of atouch dimmer is described in greater detail in commonly-assigned U.S.Pat. No. 5,196,782, issued Mar. 23, 1993, entitled TOUCH-OPERATED POWERCONTROL, the entire disclosure of which is hereby incorporated byreference.

FIG. 2 is a cross-sectional view of a prior art touch-operated device30, specifically, a membrane voltage divider. A conductive element 32and a resistive element 34 are co-extensively supported in closeproximity by a spacing frame 36. An input voltage, V_(IN), is appliedacross the resistive element 34 to provide a voltage gradient across itssurface. When pressure is applied at a point 38 along the conductiveelement 32 (by a finger or the like), the conductive element flexesdownward and electrically contacts a corresponding point along thesurface of the resistive element 34, providing an output voltage,V_(OUT), whose value is between the input voltage V_(IN) and ground.When pressure is released, the conductive element 32 recovers itsoriginal shape and becomes electrically isolated from the resistiveelement 34. The touch-operated device 30 is characterized by a contactresistance R_(CONTACT) between the conductive element 32 and theresistive element 34. The contact resistance R_(CONTACT) is dependentupon the force of the actuation of the touch-operated device 30 and istypically substantially small for a normal actuation force.

FIG. 3 is a perspective view of a user interface of a prior art touchdimmer 40. The dimmer 40 comprises a touch-operated device 30, which islocated directly behind a faceplate 42. The faceplate 42 includes aflexible area 44 located directly above the conductive element 32 of thetouch-operated device 30 to permit a user to actuate the touch-operateddevice through the faceplate 42. A conventional phase-control dimmingcircuit is located within an enclosure 46 and controls the power from asource to a load in accordance with pressure applied to a selectablepoint on flexible area 44. The faceplate 42 may include optionalmarkings 48, 50, 52 to indicate, respectively, the location of flexiblearea 44, the lowest achievable intensity level of the load, and locationof a “power off” control. An optional LED array 54 provides a visualindication of intensity level of the load. When the load is a lightsource, there is preferably a linear relationship between the number ofilluminated LEDs and the corresponding perceived light level. Theflexible area 44 may optionally include a light transmissive areathrough which LED array 54 is visible.

It is desirable to provide a touch dimmer that is responsive to only theposition of an actuation on the operational area, e.g., the flexiblearea 44 of the touch dimmer 40. However, most prior art touch dimmersare responsive to both the force and the position of a point actuation.For example, when a user lightly presses the touch-operated device 30,i.e., with a low actuation force, the contact resistance _(RCONTACT) issubstantially larger than during a normal actuation. Accordingly, theoutput of the touch-operated device 30 is not representative of theposition of the actuation and the dimmer 40 may control the lightingload to an undesired intensity level. Therefore, there is a need for atouch dimmer having an operational area that is not responsive to lighttouches and is responsive to only the position of a point actuation.

SUMMARY OF THE INVENTION

According to the present invention, a load control device forcontrolling the amount of power delivered to an electrical load from anAC power source, comprises a semiconductor switch, a controller, a touchsensitive actuator, and a stabilizing circuit. The semiconductor switchis operable to be coupled in series electrical connection between thesource and the load, the semiconductor switch having a control input forcontrolling the semiconductor switch between a non-conductive state anda conductive state. The controller is operatively coupled to the controlinput of the semiconductor switch for controlling the semiconductorswitch between the non-conductive state and the conductive state. Thetouch sensitive actuator has a touch sensitive front surface responsiveto a point actuation characterized by a position and a force. The touchsensitive actuator has an output operatively coupled to the controllerfor providing a control signal to the controller. The stabilizingcircuit is coupled to the output of the touch sensitive actuator. Thecontrol signal is responsive only to the position of the pointactuation.

According to a second embodiment of the present invention, a loadcontrol device for controlling the amount of power delivered to anelectrical load from an AC power source, the load control devicecomprises a semiconductor switch, a controller, a touch sensitiveactuator, a usage detection circuit, and a stabilizing circuit. Thesemiconductor switch is operable to be coupled in series electricalconnection between the source and the load. The semiconductor switch hasa control input for controlling the semiconductor switch between anon-conductive state and a conductive state. The controller isoperatively coupled to the control input of the semiconductor switch forcontrolling the semiconductor switch between the non-conductive stateand the conductive state. The touch sensitive actuator having a touchsensitive front surface responsive to a point actuation characterized bya position and a force, the touch sensitive actuator having an outputfor providing a control signal. The usage detection circuit isoperatively coupled between the output of the touch sensitive actuatorand the controller for determining whether the point actuation ispresently occurring. The stabilizing circuit is operatively coupledbetween the output of the touch sensitive actuator and the controllerfor stabilizing the control signal from the output of the touchsensitive actuator. The controller is responsive to the control signalwhen the usage detection circuit has determined that the point actuationis presently occurring.

According to another aspect of the present invention, in a controlcircuit for operating an electrical load in response to an output signalfrom a touch pad, said touch pad comprising an elongated manuallytouchable resistive area which produces an output signal at an outputterminal, said signal representative of the location at which the touchpad is manually touched, said control circuit including a microprocessorhaving an input connected to said output signal and producing an outputfor controlling said load in response to the manual input to said touchpad, the improvement comprising a filter capacitor connected betweensaid output terminal and a ground terminal to define aresistive-capacitive circuit with the resistance of said touch pad, saidresistive-capacitive circuit characterized by a time constant and beingadapted to prevent large transient voltage changes due to low pressuretouches of said touch pad.

Further, in a manually operable control structure for producing anelectrical signal dependent on the location at which a touch screen istouched; said control structure comprising a resistive touch screenhaving a control voltage connected to terminals at its opposite ends andan output terminal which is connected to said touch screen at thelocation of a local manual pressure applied to said screen by a user; amicroprocessor having an input connected to said output terminal andproducing an output related to the position at which said screenreceives said local manual pressure; the improvement which comprises afilter capacitor connected between said output terminal and a groundterminal and defining an R/C circuit with the resistance of said touchscreen between said position at which said screen receives local manualpressure and one of its said terminals.

In addition, the present invention provides a process for generating anoperating signal from a resistive touch screen in which an outputvoltage on a output terminal is related to both the location on thescreen area which is touched by a users finger and to the pressure ofthe touch; said process comprising the production of an x signal inresponse to the touching of said screen at any location on its surfaceand the production of a y signal in response to the location at whichthe screen is touched, and applying said x and y signals to amicroprocessor; said microprocessor producing an output signal to acircuit to be controlled only when an x output signal is present and a youtput signal is also present at the end of a predetermined sampleinterval.

Other features and advantages of the present invention will becomeapparent from the following description of the invention that refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a user interface of a prior art dimmer;

FIG. 2 is a cross-sectional view of a prior art touch-operated device;

FIG. 3 is a perspective view of a user interface of a prior art touchdimmer;

FIG. 4A is a perspective view of a touch dimmer according to the presentinvention;

FIG. 4B is a front view of the touch dimmer of FIG. 4A;

FIG. 5A is a partial assembled sectional view of a bezel and the touchsensitive device of the touch dimmer of FIG. 4A;

FIG. 5B is a partial exploded sectional view of the bezel and the touchsensitive device of FIG. 5A;

FIG. 6 shows the force profiles of the components and a cumulative forceprofile of the touch dimmer of FIG. 4A;

FIG. 7 is a simplified block diagram of the touch dimmer of FIG. 4A;

FIG. 8 is a simplified schematic diagram of a stabilizing circuit and ausage detection circuit of the touch dimmer of FIG. 7 according to afirst embodiment of the present invention;

FIG. 9 is a simplified schematic diagram of an audible sound generatorof the touch dimmer of FIG. 7;

FIG. 10 is a flowchart of a touch dimmer procedure executed by acontroller of the dimmer of FIG. 4A;

FIG. 11 is a flowchart of an Idle procedure of the touch dimmerprocedure of FIG. 10;

FIGS. 12A and 12B are flowcharts of an ActiveHold procedure of the touchdimmer procedure of FIG. 10;

FIG. 13 is a flowchart of a Release procedure of the touch dimmerprocedure of FIG. 10;

FIGS. 14A and 14B are simplified schematic diagrams of the circuitry fora four wire touch sensitive device and a controller of the touch dimmerof FIG. 4A according to a second embodiment of the present invention;

FIG. 15A is a simplified schematic diagram of the circuitry for a fourwire touch sensitive device and a controller of the touch dimmer of FIG.4A according to a third embodiment of the present invention;

FIG. 15B is a simplified block diagram of a dimmer according to a fourthembodiment of the present invention;

FIG. 15C is a simplified schematic diagram of the circuitry for athree-wire touch sensitive device and a controller of the dimmer of FIG.15B.

FIG. 16A is a perspective view of a touch dimmer according to a fifthembodiment of the present invention;

FIG. 16B is a front view of the touch dimmer of FIG. 16A;

FIG. 17A is a bottom cross-sectional view of the touch dimmer of FIG.16B;

FIG. 17B is an enlarged partial view of the bottom cross-sectional viewof FIG. 17A;

FIG. 18A is a left side cross-sectional view of the touch dimmer of FIG.16B;

FIG. 18B is an enlarged partial view of the left side cross-sectionalview FIG. 18A;

FIG. 19 is a perspective view of a display printed circuit board of thedimmer of FIG. 16A; and

FIG. 20 is an enlarged partial bottom cross-sectional view of a thintouch sensitive actuator according to a sixth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing summary, as well as the following detailed description ofthe preferred embodiments, is better understood when read in conjunctionwith the appended drawings. For the purposes of illustrating theinvention, there is shown in the drawings an embodiment that ispresently preferred, in which like numerals represent similar partsthroughout the several views of the drawings, it being understood,however, that the invention is not limited to the specific methods andinstrumentalities disclosed.

FIGS. 4A and 4B are a perspective view and a front view, respectively,of a touch dimmer 100 according to the present invention. The dimmer 100includes a faceplate 102, i.e., a cover plate, having a planar frontsurface 103 and an opening 104. The opening 104 may define a standardindustry-defined opening, such as a traditional opening or a decoratoropening, or another uniquely-sized opening as shown in FIG. 4A. A bezel106 having a planar touch sensitive front surface 108 extends throughthe opening 104 of the faceplate 102. The front surface 108 of the bezel106 is positioned immediately above a touch sensitive device 110 (shownin FIGS. 5A and 5B), i.e., a touch sensitive element, such that a userof the dimmer 100 actuates the touch sensitive element 110 by pressingthe front surface 108 of the bezel 106. As shown in FIG. 4A, the frontsurface 108 of the bezel 106 is substantially flush with the frontsurface 103 of the faceplate 102, i.e., the plane of the front surface108 of the bezel 106 is coplanar with the plane of the front surface 103of the faceplate 102. However, the bezel 106 may extend through theopening 104 of the faceplate 102 such that the front surface 108 of thebezel is provided in a plane above the plane of the front surface 103 ofthe faceplate 102. The faceplate 102 is connected to an adapter 109,which is connected to a yoke (not shown). The yoke is adapted to mountthe dimmer 100 to a standard electrical wallbox.

The dimmer 100 further comprises a visual display, e.g., a plurality ofstatus markers 112 provided in a linear array along an edge of the frontsurface 108 of the bezel 106. The status markers 112 are preferablyilluminated from behind by status indicators 114, e.g., light-emittingdiodes (LEDs), located internal to the dimmer 100 (see FIG. 7). Thedimmer 100 preferably comprises a light pipe (not shown) having aplurality of light conductors to conduct the light from the statusindicators 114 inside the dimmer to the markers 112 on the front surface108 of the bezel 106. The status indicators 114 behind the markers 112are preferably blue. As shown in FIGS. 4A and 4B, the dimmer 100comprises seven (7) status markers 112. However, the dimmer 100 maycomprise any number of status markers. Further, the status markers 112may be disposed in a vertical linear array along the center of the frontsurface 108 of the bezel 106. The markers 112 may comprise shadowsapparent on the front surface 108 due to voids behind the front surface.

The front surface 108 of the bezel 106 further includes an icon 116. Theicon 116 may be any sort of visual marker, such as, for example, a dot.Upon actuation of the lower portion of the front surface 108 surroundingthe icon 116, the dimmer 100 causes a connected lighting load 208 (FIG.7) to change from on to off (and vice versa), i.e., to toggle.Preferably, a blue status indicator and an orange status indicator arelocated immediately behind the icon 116, such that the icon 116 isilluminated with blue light when the lighting load 208 is on andilluminated with orange light when the lighting load is off. Actuationof the upper portion of the front surface 108, i.e., above the portionsurrounding the icon 116, causes the intensity of the lighting load 208to change. The status indicators 114 behind the status markers 112 areilluminated to display the intensity of the lighting load 208. Forexample, if the lighting load 208 is at 50% lighting intensity, themiddle status indicator will be illuminated. Preferably, the dimmer 100does not respond to actuations in a keepout region 118 of the frontsurface 108. The keepout region 118 prevents inadvertent actuation of anundesired portion of the front surface 108 during operation of thedimmer 100.

The dimmer 100 further includes an airgap switch actuator 119. Pullingthe airgap switch actuator 119 opens a mechanical airgap switch 219(FIG. 7) inside the dimmer 100 and disconnects the lighting load 208from a connected AC voltage source 204 (FIG. 7). The airgap switchactuator 119 extends only sufficiently above the front surface 103 ofthe faceplate 102 to be gripped by a fingernail of a user. Theelectronic circuitry of the dimmer 100 (to be described in greaterdetail below) is mounted on a printed circuit board (PCB) (not shown).The PCB is housed in an enclosure (not shown), i.e., an enclosed volume,which is attached to the yoke of the dimmer 100.

FIG. 5A is a partial assembled sectional view and FIG. 5B is a partialexploded sectional view of the bezel 108 and the touch sensitive device110 of the dimmer 100 according to the present invention. The touchsensitive device 110 comprises, for example, a resistive divider, andoperates in a similar fashion as the touch-operated device 30 of theprior art touch dimmer 40. The touch sensitive device 110 includes aconductive element 120 and a resistive element 122 supported by aspacing frame 124. However, the touch sensitive device 110 may comprisea capacitive touch screen or any other type of touch responsive element.Such touch sensitive devices are often referred to as touch pads ortouch screens.

An elastomer 126 is received by an opening 128 in the rear surface ofthe bezel 106. The elastomer 126 is positioned between the bezel 106 andthe touch sensitive device 110, such that a press on the front surface108 of the bezel is transmitted to the conductive element 120 of thetouch sensitive device 110. Preferably, the elastomer 126 is made ofrubber and is 0.040″ thick. The elastomer 126 preferably has a durometerof 40A, but may have a durometer in the range of 20A to 80A. Theconductive element 120 and the resistive element 122 of the touchsensitive device 110 and the elastomer 126 are preferably manufacturedfrom a transparent material such that the light from the plurality ofstatus indicators 114 inside the dimmer 100 are operable to shinethrough the touch sensitive device 110 and the elastomer 126 to frontsurface 108 of the bezel 106.

The position and size of the touch sensitive device 110 is demonstratedby the dotted line in FIG. 4B. The touch sensitive device 110 has alength L₁ and a width W₁ that is larger than a length L₂ and a width W₂of the front surface 108 of the bezel 106. Accordingly, a first area A₁of the surface of touch sensitive device 110 (i.e., A₁=L₁·W₁) is greaterthan a second area A₂ of the front surface 108 of the bezel 106 (i.e.,A₂=L₂·W₂). An orthogonal projection of the second area A₂ onto the firstarea A₁ is encompassed by the first area A₁, such that a point actuationat any point on the front surface 108 of the bezel 106 is transmitted tothe conductive element 120 of the touch sensitive device 110. As shownin FIGS. 4A and 4B, the length L₂ of the front surface 108 of the bezel106 is approximately four (4) times greater than the width W₂.Preferably, the length L₂ of the front surface 108 of the bezel 106 isfour (4) to six (6) times greater than the width W₂. Alternatively, thefront surface 108 of the bezel 106 may be provided in an opening of adecorator-style faceplate

FIG. 6 shows the force profiles of the components of the dimmer 100shown in FIGS. 5A and 5B and a cumulative force profile for the touchsensitive device 110 of the dimmer 100. Each of the force profiles showsthe force required to actuate the touch sensitive device 110 withrespect to the position of the point actuation. The force profilerepresents the amount of force required to displace the element by agiven amount. While the force profiles in FIG. 6 are shown with respectto the widths of the components of the dimmer 100, a similar forceprofile is also provided along the length of the components.

FIG. 6( a) shows a force profile of the bezel 106. The bezel 106 hassubstantially thin sidewalls 129, e.g., 0.010″ thick, such that thebezel 106 exhibits a substantially flat force profile. FIG. 6( b) showsa force profile of the touch sensitive device 110. The force required toactuate the touch sensitive device 110 increases near the edges becauseof the spacing frames 124. FIG. 6( c) shows a force profile of theelastomer 126. The force profile of the elastomer 126 is substantiallyflat, i.e., a force at any point on the front surface of the elastomer126 will result in a substantially equal force at the correspondingpoint on the rear surface.

FIG. 6( d) is a total force profile of the touch dimmer 100. Theindividual force profiles shown in FIGS. 6( a)-(c) are additive tocreate the total force profile. The total force profile is substantiallyflat across the second area A₂ of the front surface 108 of the bezel106. This means that a substantially equal minimum actuation forcef_(MIN) is required to actuate the touch sensitive device 110 at allpoints of the front surface 108 of the bezel 106, even around the edges.Accordingly, the dimmer 100 of the present invention provides a maximumoperational area in an opening of a faceplate, i.e., substantially allof the second area A₂ of the front surface 108 of the bezel 106, whichis an improvement over the prior art touch dimmers. The minimumactuation force f_(MIN) is substantially equal at all points on thefront surface 108 of the bezel 106. For example, the minimum actuationforce f_(MIN) may be 20 grams.

FIG. 7 is a simplified block diagram of the touch dimmer 100 accordingto the present invention. The dimmer 100 has a hot terminal 202connected to an AC voltage source 204 and a dimmed hot terminal 206connected to a lighting load 208. The dimmer 100 employs a bidirectionalsemiconductor switch 210 coupled between the hot terminal 202 and thedimmed hot terminal 206, to control the current through, and thus theintensity of, the lighting load 208. The semiconductor switch 210 has acontrol input (or gate), which is connected to a gate drive circuit 212.The input to the gate renders the semiconductor switch 210 selectivelyconductive or non-conductive, which in turn controls the power suppliedto the lighting load 208. The gate drive circuit 212 provides a controlinput to the semiconductor switch 210 in response to a control signalfrom a controller 214. The controller 214 may be any suitablecontroller, such as a microcontroller, a microprocessor, a programmablelogic device (PLD), or an application specific integrated circuit(ASIC).

A zero-crossing detect circuit 216 determines the zero-crossing pointsof the AC source voltage from the AC power supply 204. A zero-crossingis defined as the time at which the AC supply voltage transitions frompositive to negative polarity, or from negative to positive polarity, atthe beginning of each half-cycle. The zero-crossing information isprovided as an input to the controller 214. The controller 214 generatesthe gate control signals to operate the semiconductor switch 210 to thusprovide voltage from the AC power supply 204 to the lighting load 208 atpredetermined times relative to the zero-crossing points of the ACwaveform. A power supply 218 generates a direct-current (DC) voltageV_(CC), e.g., 5 volts, to power the controller 214 and other low voltagecircuitry of the dimmer 100.

The touch sensitive device 110 is coupled to the controller 214 througha stabilizing circuit 220 and a usage detection circuit 222. Thestabilizing circuit 220 is operable to stabilize the voltage output ofthe touch sensitive device 110. Accordingly, the voltage output of thestabilizing circuit 220 is not dependent on the magnitude of the forceof the point actuation on the touch sensitive device 110, but rather isdependent solely on the position of the point actuation. The usagedetection circuit 222 is operable to detect when a user is actuating thefront surface 108 of the dimmer 100. The controller 214 is operable tocouple and decouple the stabilizing circuit 220 and the usage detectioncircuit 222 from the output of the touch sensitive device 110. Thecontroller is further operable to receive control signals from both thestabilizing circuit 220 and the usage detection circuit 222. Preferably,the stabilizing circuit 220 has a slow response time, while the usagedetection circuit 222 has a fast response time. Thus, the controller 214is operable to control the semiconductor switch 210 in response to thecontrol signal provided by the stabilizing circuit 220 when the usagedetection circuit 222 has detected an actuation of the touch sensitivedevice 110.

The controller 214 is operable to drive the plurality of statusindicators 114, e.g., light-emitting diodes (LEDs), which are locatedbehind the markers 112 on the front surface 108 of the dimmer 100. Thestatus indicators 114 also comprise the blue status indicator and theorange status indicator that are located immediately behind the icon116. The blue status indicator and the orange status indicator may beimplemented as separate blue and orange LEDs, respectively, or as asingle bi-colored LED.

The dimmer 100 further comprises an audible sound generator 224 coupledto the controller 214, such that the controller is operable to cause thesound generator to produce an audible sound in response to an actuationof the touch sensitive device 110. A memory 225 is coupled to thecontroller 214 and is operable to store control information of thedimmer 100.

FIG. 8 is a simplified schematic diagram of the circuitry for the touchsensitive device 110 and the controller 214, i.e., the stabilizingcircuit 220 and the usage detection circuit 222, according to a firstembodiment of the present invention. The resistive element 122 of thetouch sensitive device 110 is coupled between the DC voltage V_(CC) ofthe power supply 218 and circuit common, such that the DC voltage V_(CC)provides a biasing voltage to the touch sensitive device. For example,the resistive element 122 may have a resistance R_(E) of 7.6 kΩ. Theposition of contact between the conductive element 120 and the resistiveelement 122 of the touch sensitive device 110 is determined by theposition of a point actuation on the front surface 108 of the bezel 106of the dimmer 100. The conductive element 120 is coupled to both thestabilizing circuit 220 and the usage detection circuit 222. As shown inFIG. 7, the touch sensitive device 110 of the dimmer 100 of the firstembodiment is a three-wire device, i.e., the touch sensitive device hasthree connections or electrodes. The touch sensitive device provides oneoutput that is representative of the position of the point actuationalong a Y-axis, i.e., a longitudinal axis of the dimmer 100 as shown inFIG. 4B.

The stabilizing circuit 220 comprises a whacking-grade capacitor C230(that is, a capacitor having a large value of capacitance) and a firstswitch 232. The controller 214 is operable to control the first switch232 between a conductive state and a non-conductive state. When thefirst switch 232 is conductive, the capacitor C230 is coupled to theoutput of the touch sensitive device 110, such that the output voltageis filtered by the capacitor C230. When a touch is present, the voltageon the capacitor C230 will be forced to a steady-state voltagerepresenting the position of the touch on the front surface 108. When notouch is present, the voltage on the capacitor will remain at a voltagerepresenting the position of the last touch. The touch sensitive device110 and the capacitor C230 form a sample-and-hold circuit. The responsetime of the sample-and-hold circuit is determined by a resistance R_(D)of the touch sensitive device (i.e., the resistance R_(E) of theresistive element and a contact resistance R_(C)) and the capacitance ofthe capacitor C230. During typical actuation, the contact resistanceR_(C) is small compared to the value of R_(E), such that a firstcharging time constant τ₁ is approximately equal to R_(E)·C₂₃₀. Thistime constant τ₁ is preferably 13 ms, but may be anywhere between 6 msand 15 ms.

When a light or transient press is applied to the touch sensitive device110, the capacitor C230 will continue to hold the output at the voltagerepresenting the position of the last touch. During the release of thetouch sensitive device 110, transient events may occur that produceoutput voltages that represent positions other than the actual touchposition. Transient presses that are shorter than the first chargingtime constant τ₁ will not substantially affect the voltage on thecapacitor C230, and therefore will not substantially affect the sensingof the position of the last actuation. During a light press, a secondcharging time constant τ₂ will be substantially longer than duringnormal presses, i.e., substantially larger than the first time constantτ₁, due to the higher contact resistance R_(C). However, thesteady-state value of the voltage across the capacitor C230 will be thesame as for a normal press at the same position. Therefore, the outputof the stabilizing circuit 220 is representative of only the position ofthe point of actuation of the touch sensitive device 110.

The usage detection circuit 222 comprises a resistor R234, a capacitorC236, and a second switch 238, which is controlled by the controller214. When the switch 238 is conductive, the parallel combination of theresistor R234 and the capacitor C236 is coupled to the output of thetouch sensitive device 110. Preferably, the capacitor C236 has asubstantially small capacitance C₂₃₆, such that the capacitor C236charges substantially quickly in response to all point actuations on thefront surface 108. The resistor R234 allows the capacitor C236 todischarge quickly when the switch 238 is non-conductive. Therefore, theoutput of the usage detection circuit 222 is representative of theinstantaneous usage of the touch sensitive device 110.

The controller 214 controls the switches 232, 238 in a complementarymanner. When the first switch 232 is conductive, the second switch 238is non-conductive, and vice versa. The controller 214 controls thesecond switch 238 to be conductive for a short period of time _(tUsAGE)once every half cycle of the voltage source 204 to determine whether theuser is actuating the front surface 108. Preferably, the short period oftime t_(USAGE) is approximately 100 μsec or 1% of the half-cycle(assuming each half-cycle is 8.33 msec long). For the remainder of thetime, the first switch 232 is conductive, such that the capacitor C230is operable to charge accordingly. When the first switch 232 isnon-conductive and the second switch 238 is conductive, thewhacking-grade capacitor C230 of the stabilizing circuit 220 is unableto discharge at a significant rate, and thus the voltage developedacross the capacitor C230 will not change significantly when thecontroller 214 is determining whether the touch sensitive device 110 isbeing actuated through the usage detection circuit 222. While thestabilizing circuit 220 is shown and described as a hardware circuit inthe present application, the controller 214 could alternatively providethe filtering functionality of the stabilizing circuit entirely insoftware.

FIG. 9 is a simplified schematic diagram of the audible sound generator224 of the dimmer 100. The audible sound generator 224 uses an audiopower amplifier integrated circuit (IC) 240, for example, part numberTPA721 manufactured by Texas Instruments, Inc., to generate a sound froma piezoelectric or magnetic speaker 242. The amplifier IC 240 is coupledto the DC voltage V_(CC) (pin 6) and circuit common (pin 7) to power theamplifier IC. A capacitor C244 (preferably having a capacitance of 0.1μF) is coupled between the DC voltage V_(CC) and circuit common todecouple the power supply voltage and to ensure the output totalharmonic distortion (THD) is as low as possible.

The audible sound generator 224 receives a SOUND ENABLE signal 246 fromthe controller 214. The SOUND ENABLE signal 246 is provided to an enablepin (i.e., pin 1) on the amplifier IC 240, such that the audible soundgenerator 224 will be operable to generate the sound when the SOUNDENABLE signal is at a logic high level.

The audible sound generate 224 further receives a SOUND WAVE signal 248from the controller 214. The SOUND WAVE signal 248 is an audio signalthat is amplified by the amplifier IC 240 to generate the appropriatesound at the speaker 242. The SOUND WAVE signal 248 is first filtered bya low-pass filter comprising a resistor R250 and a capacitor C252.Preferably, the resistor R250 has a resistance of 1 kΩ and the capacitorC252 has a capacitance of 0.1 nF. The filtered signal is then passedthrough a capacitor C254 to produce an input signal V_(IN). Thecapacitor C254 allows the amplifier IC to bias the input signal V_(IN)to the proper DC level for optimum operation and preferably has acapacitance of 0.1 μF. The input signal V_(IN) is provided to a negativeinput (pin 4) of the amplifier IC 240 through a input resistor R_(I). Apositive input (pin 3) of the amplifier IC 240 and with a bypass pin(pin 2) are coupled to circuit common through a bypass capacitor C256(preferably, having a capacitance of 0.1 μF).

The output signal V_(OUT) of the amplifier IC 240 is produced from apositive output (pin 5) to a negative output (pin 8) and is provided tothe speaker 242. The negative input (pin 4) is coupled to the positiveoutput (pin 5) through an output resistor R_(F). The gain of theamplifier IC 240 is set by the input resistor R_(I) and the feedbackresistor R_(F), i.e.,

Gain=V _(OUT) /V _(IN)=−2·(R _(F) / R _(I)).

Preferably, the input resistor R_(I) and the output resistor R_(F) bothhave resistances of 10 kΩ, such that the gain of the amplifier IC 240 isnegative two (−2).

FIG. 10 is a flowchart of a touch dimmer procedure 300 executed by thecontroller 214 of the dimmer 100 according to the present invention.Preferably, the touch dimmer procedure 300 is called from the main loopof the software of the controller 214 once every half cycle of the ACvoltage source 204. The touch dimmer procedure 300 selectively executesone of three procedures depending upon the state of the dimmer 100. Ifthe dimmer 100 is in an “Idle” state (i.e., the user is not actuatingthe touch sensitive device 110) at step 310, the controller 214 executesan Idle procedure 400. If the dimmer 100 is in an “ActiveHold” state(i.e., the user is presently actuating the touch sensitive device 110)at step 320, the controller 214 executes an ActiveHold procedure 500. Ifthe dimmer 100 is in a “Release” state (i.e., the user has recentlyceased actuating the touch sensitive device 110) at step 330, thecontroller 214 executes a Release procedure 600.

FIG. 11 is a flowchart of the Idle procedure 400 according to thepresent invention. The controller 114 uses a “sound flag” and a “soundcounter” to determine when to cause the audible sound generator 224 togenerate the audible sound. The purpose of the sound flag is to causethe sound to be generated the first time that the controller 214executes the ActiveHold procedure 500 after being in the Idle state. Ifthe sound flag is set, the controller 214 will cause the sound to begenerated. The sound counter is used to ensure that the controller 214does not cause the audible sound generator 224 to generate the audiblesound too often. The sound counter preferably has a maximum soundcounter value S_(MAX), e.g., approximately 425 msec. Accordingly, thereis a gap of approximately 425 msec between generations of the audiblesound. The sound counter is started during the Release procedure 600 aswill be described in greater detail below. Referring to FIG. 11, uponentering the Idle state, the controller 214 sets the sound flag at step404 if the sound flag is not set at step 402.

An “LED counter” and an “LED mode” are used by the controller 214 tocontrol the status indicators 114 (i.e., the LEDs) of the dimmer 100.The controller 214 uses the LED counter to determine when apredetermined time t_(LED) has expired since the touch sensitive device110 was actuated. When the predetermined time t_(LED) has expired, thecontroller 214 will change the LED mode from “active” to “inactive”.When the LED mode is “active”, the status indicators 114 are controlledsuch that one or more of the status indicators are illuminated to abright level. When the predetermined time t_(LED) expires, the LED modeis changed to “inactive”, i.e., the status indicators 114 are controlledsuch that one or more of the status indicators are illuminated to a dimlevel. Referring to FIG. 11, if the LED counter is less than a maximumLED counter value L_(MAX) at step 410, the LED counter is incremented atstep 412 and the process moves on to step 418. However, if the LEDcounter is not less than the maximum LED counter value L_(MAX), the LEDcounter is cleared at step 414 and the LED mode is set to inactive atstep 416. Since the touch dimmer procedure 300 is executed once everyhalf cycle, the predetermined time t_(LED) is preferably equal to

t _(LED) =T _(HALF) ·L _(MAX),

where T_(HALF) is the period of a half cycle.

Next, the controller 214 reads the output of the usage detection circuit222 to determine if the touch sensitive device 110 is being actuated.Preferably, the usage detection circuit 222 is monitored once every halfcycle of the voltage source 204. At step 418, the controller 214 opensswitch 232 and closes switch 238 to couple the resistor R234 and thecapacitor C236 to the output of the touch sensitive device 110. Thecontroller 214 determines the DC voltage of the output of the usagedetection circuit 222 at step 420, preferably, by using ananalog-to-digital converter (ADC). Next, the controller 214 closesswitch 232 and opens switch 238 at step 422.

At step 424, if there is activity on the front surface 108 of the dimmer100, i.e., if the DC voltage determined at step 420 is above apredetermined minimum voltage threshold, then an “activity counter” isincremented at step 426. Otherwise, the activity counter is cleared atstep 428. The activity counter is used by the controller 214 todetermine if the DC voltage determined at step 420 is the result of apoint actuation of the touch sensitive device 110 rather than noise orsome other undesired impulse. The use of the activity counter is similarto a software “debouncing” procedure for a mechanical switch, which iswell known in the art. If the activity counter is not less than amaximum activity counter value A_(MAX) at step 430, then the dimmerstate is set to the ActiveHold state at step 432. Otherwise, the processsimply exits at step 434.

FIGS. 12A and 12B are flowcharts of the ActiveHold procedure 500, whichis executed once every half cycle when the touch sensitive device 110 isbeing actuated, i.e., when the dimmer 100 is in the ActiveHold state.First, a determination is made as to whether the user has stopped using,i.e., released, the touch sensitive device 110. The controller 214 opensswitch 232 and closes switch 238 at step 510, and reads the output ofthe usage detection circuit 222 at step 512. At step 514, the controller214 closes switch 232 and opens switch 238. If there is no activity onthe front surface 108 of the dimmer 100 at step 516, the controller 214increments an “inactivity counter” at step 518. The controller 214 usesthe inactivity counter to make sure that the user is not actuating thetouch sensitive device 110 before entering the Release mode. If theinactivity counter is less than a maximum inactivity counter valueI_(MAX) at step 520, the process exits at step 538. Otherwise, thedimmer state is set to the Release state at step 522, and then theprocess exits.

If there is activity on the touch sensitive device 110 at step 516, thecontroller 214 reads the output of the stabilizing circuit 220, which isrepresentative of the position of the point actuation on the frontsurface 108 of the dimmer 100. Since the switch 232 is conductive andthe switch 238 is non-conductive, the controller 214 determines the DCvoltage at the output of the stabilizing circuit 220, preferably usingan ADC, at step 524.

Next, the controller 214 uses a buffer to “filter” the output ofstabilizing circuit 220. When a user actuates the touch sensitive device110, the capacitor C230 will charge to approximately the steady-statevoltage representing the position of the actuation on the front surface108 across a period of time determined by the first time constant τ₁ aspreviously described. Since the voltage across the capacitor C230, i.e.,the output of the stabilizing circuit 220, is increasing during thistime, the controller 214 delays for a predetermined period of time atstep 525, preferably, for approximately three (3) half cycles.

When a user's finger is removed from the front surface 108 of the bezel106, subtle changes in the force and position of the point actuationoccur, i.e., a “finger roll-off” event occurs. Accordingly, the outputsignal of the touch sensitive device 110 is no longer representative ofthe position of the point actuation. To prevent the controller 214 fromprocessing reads during a finger roll-off event, the controller 214saves the reads in the buffer and processes the reads with a delay,e.g., six half cycles later. Specifically, when the delay is over atstep 525, the controller 214 rotates the new read (i.e., from step 524)into the buffer at step 526. If the buffer has at least six reads atstep 528, the controller 214 averages the reads in the fifth and sixthpositions in the buffer at step 530 to produce the touch position data.In this way, when the user stops actuating the touch sensitive device110, the controller 214 detects this change at step 516 and sets thedimmer state to the Release state at step 522 before the controllerprocesses the reads saved in the buffer near the transition time of thetouch sensitive device.

At step 532, the controller 114 determines if the touch position datafrom step 530 is in the keepout region 118 (as shown in FIG. 4B). If thetouch position data is in the keepout region 118, the ActiveHoldprocedure 500 simply exits at step 538. Otherwise, a determination ismade at step 534 as to whether the sound should be generated.Specifically, if the sound flag is set and if the sound counter hasreached a maximum sound counter value S_(MAX), the controller 214 drivesthe SOUND ENABLE signal 246 high and provides the SOUND WAVE signal 248to the audible sound generator 224 to generate the sound at step 535.Further, the sound flag is cleared at step 536 such that the sound willnot be generated as long as the dimmer 100 remains in the ActiveHoldstate.

If the touch position data is in the toggle area, i.e., the lowerportion of the front surface 108 of the bezel 106 surrounding the icon116 (as shown in FIG. 4A), at step 540, the controller 214 processes theactuation of the touch sensitive device 110 as a toggle. If the lightingload 208 is presently off at step 542, the controller 214 turns thelighting load on. Specifically, the controller 214 illuminates the icon116 with the blue status indicator at step 544 and dims the lightingload 208 up to the preset level, i.e., the desired lighting intensity ofthe lighting load, at step 546. If the lighting load is presently on atstep 542, the controller 214 turns on the orange status indicator behindthe icon 116 at step 548 and fades the lighting load 208 to off at step550.

If the touch position data is not in the toggle area at step 540, thecontroller 214 scales the touch position data at step 552. The output ofthe stabilizing circuit 220 is a DC voltage between a maximum value,i.e., substantially the DC voltage V_(CC), and a minimum value, whichcorresponds to the DC voltage providing by the touch sensitive device110 when a user is actuating the lower end of the upper portion of thefront surface 108 of the bezel 106. The controller 214 scales this DCvoltage to be a value between off (i.e., 1%) and full intensity (i.e.,100%) of the lighting load 208. At step 554, the controller 214 dims thelighting load 208 to the scaled level produced in step 552.

Next, the controller 214 changes the status indicators 114 locatedbehind the markers 112 on the front surface 108 of the bezel 106. As auser actuates the touch sensitive device 110 to change intensity of thelighting load 208, the controller 214 decides whether to change thestatus indicator 114 that is presently illuminated. Since there areseven (7) status indicators to indicate an intensity between 1% and100%, the controller 214 may illuminate the first status indicator,i.e., the lowest status indicator, to represent an intensity between 1%and 14%, the second status indicator to represent an intensity between15% and 28%, and so on. The seventh status indicator, i.e., the higheststatus indicator, may be illuminated to represent an intensity between85% and 100%. Preferably, the controller 214 uses hysteresis to controlthe status indicators 114 such that if the user actuates the frontsurface 108 at a boundary between two of the regions of intensitiesdescribed above, consecutive status indicators do not toggle back andforth.

Referring to FIG. 12B, a determination is made as to whether a change isneeded as to which status indicator is illuminated at step 556. If thepresent LED (in result to the touch position data from step 530) is thesame as the previous LED, then no change in the LED is required. Thepresent LED is set the same as the previous LED at step 558, ahysteresis counter is cleared at step 560, and the process exits at step570.

If the present LED is not the same as the previous LED at step 556, thecontroller 214 determines if the LED should be changed. Specifically, atstep 562, the controller 214 determines if present LED would change ifthe light level changed by 2% from the light level indicated by thetouch position data. If not, the hysteresis counter is cleared at step560 and the process exits at step 570. Otherwise, the hysteresis counteris incremented at step 564. If the hysteresis counter is less than amaximum hysteresis counter value H_(MAX) at step 566, the process exitsat step 570. Otherwise, the LEDs are changed accordingly based on thetouch position data at step 568.

FIG. 13 is a flowchart of the Release procedure 600, which is executedafter the controller 214 sets the dimmer state to the Release state atstep 522 of the ActiveHold procedure 500. First, a save flag is set atstep 610. Next, the sound counter is reset at step 612 to ensure thatthe sound will not be generated again, e.g., for preferably 18 halfcycles. At step 618, a determination is made as to whether the dimmer100 is presently executed a fade-to-off. If not, the present level issaved as the preset level in the memory 225 at step 620. Otherwise, thedesired lighting intensity is set to off at step 622, the long fadecountdown in started at step 624, and the preset level is saved as offin the memory 225.

FIG. 14A and FIG. 14B are simplified schematic diagrams of the circuitryfor a four-wire touch sensitive device 710 and a controller 714according to a second embodiment of the present invention. The four-wiretouch sensitive device 710 has four connections, i.e., electrodes, andprovides two outputs: a first output representative of the position of apoint actuation along the Y-axis, i.e., the longitudinal axis of thedimmer 100 a shown in FIG. 4B, and a second output representative of theposition of the point actuation along the X-axis, i.e., an axisperpendicular to the longitudinal axis. The four-wire touch sensitivedevice 710 provides the outputs depending on how the DC voltage V_(CC)is connected to the touch sensitive device. A stabilizing circuit 720 isoperatively coupled to the first output and a usage detection circuit722 is operatively coupled to the second output.

The controller 714 controls three switches 760, 762, 764 to connect thetouch sensitive device 710 to the DC voltage V_(CC) accordingly. Whenthe switches 760, 762, 764 are connected in position A as shown in FIG.14A, the DC voltage V_(CC) is coupled across the Y-axis resistor, andthe X-axis resistor provides the output to the stabilizing circuit 720.When the switches 760, 762, 764 are connected in position B as shown inFIG. 14B, the DC voltage V_(CC) is coupled across the X-axis resistor,and the Y-axis resistor provides the output to the usage detectioncircuit 722. Since the controller 714 provides one output signal tocontrol whether the stabilizing circuit 720 or the usage detectioncircuit 722 is coupled to the touch sensitive device 110, the softwareexecuted by the controller 714 is the same as the software executed bythe controller 214 shown in FIGS. 10-13.

FIG. 15A is a simplified schematic diagram of the circuitry for thefour-wire touch sensitive device 710 and a controller 814 according to athird embodiment of the present invention. The controller 814 isoperable to read the position of a point actuation on the four-wiretouch sensitive device 710 along both the Y-axis and the X-axis. Whendetermining the position along the Y-axis, the controller 814 operatesthe same as the controller 714 shown in FIGS. 14A and 14B by controllingthe switches 760, 762, 764 as described above.

An additional stabilizing circuit 870 is provided for determining theposition of the point actuation along the X-axis. The additionalstabilizing circuit 870 comprises a whacking-grade capacitor C872. Thecontroller 814 controls a switch 874 to selectively switch the output ofthe X-axis between the usage detection circuit 722 and the additionalstabilizing circuit 870. The controller 814 controls the switch 874 in asimilar fashion to how the controller 214 controls the switches 232, 238(as shown in FIG. 8).

FIG. 15B is a simplified block diagram of a dimmer 1000 according to afourth embodiment of the present invention. FIG. 15C is a simplifiedschematic diagram of the circuitry for the three-wire touch sensitivedevice 110 and a controller 1014 of the dimmer 1000 according to thefourth embodiment. The dimmer 1000 comprises only a stabilizing circuit1020 and does not comprise a usage detection circuit. The stabilizingcircuit 1020 only comprises a whacking-grade capacitor C1030.Accordingly, the controller 1014 is not operable to control thestabilizing circuit 1020 and is responsive to the touch sensitive device100 through only the stabilizing circuit.

FIGS. 16A and 16B are a perspective view and a front view, respectively,of a touch dimmer 900 according to a fifth embodiment of the presentinvention. FIG. 17A is a bottom cross-sectional view and FIG. 17B is anenlarged partial bottom cross-sectional view of the dimmer 900. FIG. 18Ais a left side cross-sectional view and FIG. 18B is an enlarged partialleft side cross-sectional view of the dimmer 900.

The touch dimmer 900 includes a thin touch sensitive actuator 910comprising an actuation member 912 extending through a bezel 914. Thedimmer 900 further comprises a faceplate 916, which has a non-standardopening 918 and mounts to an adapter 920. The bezel 914 is housed behindthe faceplate 916 and extends through the opening 918. The adapter 920connects to a yoke 922, which is adapted to mount the dimmer 900 to astandard electrical wallbox. A main printed circuit board (PCB) 924 ismounted inside an enclosure 926 and includes the some of the electricalcircuitry of the dimmer 200, e.g., the semiconductor switch 210, thegate drive circuit 212, the controller 214, the zero-crossing detectcircuit 216, the power supply 218, the stabilizing circuit 220, theusage detection circuit 222, the audible sound generator 224, and thememory 225, of the dimmer 200. The thin touch sensitive actuator 910preferably extends beyond the faceplate by 1/16″, i.e., has a height of1/16″, but may have a height in the range of 1/32″ to 3/32″. Preferably,the touch sensitive actuator 910 has a length of 3⅝″ and a width of3/16″. However, the length and the width of the touch sensitive actuator910 may be in the ranges of 2⅝″-4″ and ⅛″-¼″, respectively.

The touch sensitive actuator 910 operates to contact a touch sensitivedevice 930 inside the touch dimmer 900. The touch sensitive device 930is contained by a base 932. The actuation member 912 includes aplurality of long posts 934, which contact the front surface of thetouch sensitive device 930 and are arranged in a linear array along thelength of the actuation member. The posts 934 act as force concentratorsto concentrate the force from an actuation of the actuation member 912to the touch sensitive device 930.

A plurality of status indicators 936 are arranged in a linear arraybehind the actuation member 912. The status indicators are mounted on adisplay PCB 938, i.e., a status indicator support board, which ismounted between the touch sensitive device 930 and the bezel 914. FIG.19 is a perspective view of the display PCB 938. The display PCB 938includes a plurality of holes 939, which the long posts 934 extendthrough to contact the touch sensitive device 930. The actuation member912 is preferably constructed from a translucent material such that thelight of the status indicators 936 is transmitted to the surface of theactuation member. A plurality of short posts 940 are provided in theactuation member 912 directly above the status indicators 936 to operateas light pipes for the linear array of status indicators. The displayPCB 938 comprises a tab 952 having a connector 954 on the bottom sidefor connecting the display PCB 938 to the main PCB 924.

The actuation member 912 comprises a notch 942, which separates a lowerportion 944 and an upper portion 946 of the actuation member. Uponactuation of the lower portion 944 of the actuation member 912, thedimmer 900 causes the connected lighting load to toggle from on to off(and vice versa). Preferably, a blue status indicator 948 and an orangestatus indicator 950 are located behind the lower portion 944, such thatthe lower portion is illuminated with blue light when the lighting loadis on and illuminated with orange light with the lighting load is off.Actuation of the upper portion 946 of the actuation member 912, i.e.,above the notch 942, causes the intensity of the lighting load to changeto a level responsive to the position of the actuation on the actuationmember 912. The status indicators 936 behind the status markers 112 areilluminated to display the intensity of the lighting load as with thepreviously-discussed touch dimmer 100.

FIG. 20 is an enlarged partial bottom cross-sectional view of a thintouch sensitive actuator 960 according to a sixth embodiment of thepresent invention. The touch sensitive actuator 960 comprises anactuation member 962 having two posts 964 for actuating the touchsensitive device 930. A plurality of status indicators 966 are mountedon a flexible display PCB 968, i.e., a flexible status indicator supportboard, which the posts 964 of the actuation member 962 are operable toactuate the touch sensitive device 930 through. The status indicators966 are preferably blue LEDs and are arranged along the length of theactuation member 962. Preferably, the actuation member 962 isconstructed from a translucent material such that the light of thestatus indicators 966 is transmitted to the surface of the actuationmember.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

1. A load control device for controlling an amount of power delivered toan electrical load from an AC power source, the load control devicecomprising: a semiconductor switch operable to be coupled in serieselectrical connection between the source and the load, the semiconductorswitch having a control input for controlling the semiconductor switchbetween a non-conductive state and a conductive state; a controlleroperatively coupled to the control input of the semiconductor switch forcontrolling the semiconductor switch between the non-conductive stateand the conductive state; a touch sensitive front surface; a touchsensitive device responsive to a point actuation on the touch sensitivefront surface, the point actuation characterized by a position and aforce, the touch sensitive device comprising a resistive divider and anoutput operatively coupled to the controller for providing a controlsignal to the controller; and a capacitor coupled to the output of thetouch sensitive device for stabilizing the control signal; wherein thecapacitor is operable to charge and discharge through the resistivedivider of the touch sensitive device, such that the control signal isrepresentative of the position of the point actuation.
 2. The loadcontrol device of claim 1, wherein the control signal is a DC voltageand is provided at the output of the touch sensitive device, and furtherwherein the DC voltage is representative of the position of the pointactuation, and the capacitor is operable to stabilize the DC voltage. 3.The load control device of claim 2, wherein the resistive divider of thetouch sensitive device and the capacitor form a sample-and-hold circuitdefining a time constant.
 4. The load control device of claim 3, whereinthe time constant of the sample- and-hold circuit ranges fromapproximately 6 milliseconds to 15 milliseconds.
 5. The load controldevice of claim 4, wherein the time constant is approximately 13milliseconds.
 6. The load control device of claim 2, wherein thecontroller is operable to filter the DC voltage provided by the touchsensitive device.
 7. The load control device of claim 1, wherein the DCvoltage is representative of the position of the point actuation along alongitudinal axis of the touch sensitive front surface.
 8. The loadcontrol device of claim 1, wherein the DC voltage is only representativeof the position of the point actuation when a magnitude of the force ofthe point actuation is above a predetermined level.
 9. A user interfacefor a lighting control, the user interface comprising: a touch sensitivefront surface having a longitudinal axis; a touch sensitive deviceresponsive to a point actuation on the touch sensitive front surface,the point actuation characterized by a force and a position along thelongitudinal axis of the touch sensitive front surface, the touchsensitive device comprising a resistive divider and an output forproviding a control signal; and a capacitor coupled to the output of thetouch sensitive device for stabilizing the control signal; wherein thecapacitor is operable to charge and discharge through the resistivedivider of the touch sensitive device, such that the control signal isrepresentative of the position of the point actuation.
 10. The userinterface of claim 9, wherein the control signal comprises a DC voltageprovided at the output of the touch sensitive device, the DC voltagerepresentative of the position of the point actuation, the capacitoroperable to stabilize the DC voltage.
 11. The user interface of claim10, further comprising: a usage detection circuit operatively coupled tothe touch sensitive device to product an output representative ofwhether the point actuation is presently occurring; and a controlleroperatively coupled to receive the DC voltage from the touch sensitivedevice and the output of the usage detection circuit, and operable todetermine the position of the point actuation from the DC voltage whenthe point actuation is presently occurring.
 12. The user interface ofclaim 11, wherein the DC voltage is representative of the position ofthe point actuation along the longitudinal axis of the touch sensitivefront surface.
 13. The user interface of claim 12, wherein the usagedetection circuit is operable to determine whether the position of thepoint actuation is presently changing along a lateral axis of the touchsensitive front surface.
 14. The user interface of claim 13, wherein theoutput of the touch sensitive device comprises a first output forproviding the DC voltage representative of the position of the pointactuation along the longitudinal axis, and a second output for providinga second DC voltage representative of the position of the pointactuation along the lateral axis.
 15. The user interface of claim 14,wherein the usage detection circuit comprises a capacitor coupled inparallel with a resistor, the parallel combination of the capacitor andthe resistor operatively coupled between the second output of the touchsensitive device and a circuit common.
 16. The user interface of claim15, wherein the touch sensitive device comprises a four-wire resistivetouch pad.
 17. The user interface of claim 14, further comprising: asecond capacitor operatively coupled to the second output of the touchsensitive device for stabilizing the second DC voltage provided by thetouch sensitive device; wherein the controller is operable to determinethe position of the point actuation along the longitudinal axis inresponse to the DC voltage from the first output of the touch sensitivedevice, and to determine the position of the point actuation along thelateral axis in response to the second DC voltage.
 18. The userinterface of claim 17, wherein the DC voltages are only representativeof the position of the point actuation when a magnitude of the force ofthe point actuation is above a predetermined level.
 19. The userinterface of claim 12, wherein the usage detection circuit is operableto determine whether the position of the point actuation is presentlychanging along the longitudinal axis of the touch sensitive frontsurface.
 20. The user interface of claim 19, wherein the touch sensitivedevice comprises a single output for providing the DC voltagerepresentative of the position of the point actuation along thelongitudinal axis of the touch sensitive front surface.
 21. The userinterface of claim 20, wherein the usage detection circuit comprises acapacitor coupled in parallel with a resistor, the parallel combinationof the capacitor and the resistor operatively coupled between the outputof the touch sensitive device and a circuit common.
 22. The userinterface of claim 20, wherein the touch sensitive device comprises athree-wire resistive touch pad.
 23. The user interface of claim 10,wherein the touch sensitive device and the capacitor form asample-and-hold circuit having a time constant ranging fromapproximately 6 milliseconds to 15 milliseconds.
 24. The user interfaceof claim 23, wherein the time constant of the sample-and-hold circuit isapproximately 13 milliseconds.
 25. The user interface of claim 10,wherein the capacitance of the capacitor ranges from 4 to 10microfarads.
 26. The user interface of claim 25, wherein the capacitanceof the capacitor is approximately 9 microfarads.
 27. A load controldevice for controlling an amount of power delivered to an electricalload from an AC power source, the load control device comprising: atouch sensitive front surface; a semiconductor switch operable to becoupled in series electrical connection between the source and the load,the semiconductor switch having a control input for controlling thesemiconductor switch between a non-conductive state and a conductivestate; a controller operatively coupled to the control input of thesemiconductor switch for controlling the semiconductor switch betweenthe non-conductive state and the conductive state; a touch sensitivedevice responsive to a point actuation on the touch sensitive frontsurface, the point actuation characterized by a position and a force,the touch sensitive device comprising a resistive divider and an outputfor providing a control signal; a usage detection circuit operativelycoupled between the output of the touch sensitive device and thecontroller for determining if the point actuation is presentlyoccurring; and a stabilizing circuit operatively coupled between theoutput of the touch sensitive device and the controller, the stabilizingcircuit comprising a whacking-grade capacitor for stabilizing thecontrol signal of the touch sensitive device, the capacitor operable tocharge and discharge through the resistive divider of the touchsensitive device, such that the control signal is representative of theposition of the point actuation; wherein the controller is responsive tothe control signal only when the point actuation is presently occurring.28. The load control device of claim 27, wherein the control signalcomprises a DC voltage representative of the position of the pointactuation along a longitudinal axis of the touch sensitive frontsurface.
 29. The load control device of claim 28, wherein the usagedetection circuit is operable to determine if the position of the pointactuation is presently changing along the longitudinal axis of the touchsensitive front surface.
 30. The load control device of claim 29,wherein the touch sensitive device comprises a single output forproviding the DC voltage representative of the position of the pointactuation along the longitudinal axis of the touch sensitive frontsurface.
 31. The load control device of claim 28, wherein the usagedetection circuit is operable to determine if the position of the pointactuation is presently changing along a lateral axis of the touchsensitive front surface.
 32. The load control device of claim 31,wherein the output of the touch sensitive device comprises a firstoutput for providing a first DC voltage representative of the positionof the point actuation along the longitudinal axis, and a second outputfor providing a second DC voltage representative of the position of thepoint actuation along the lateral axis.
 33. A user interface for alighting control, the user interface comprising: a touch sensitive frontsurface; a touch sensitive device responsive to a point actuation on thetouch sensitive front surface, the point actuation characterized by aposition and a force, the touch sensitive device comprising a resistivedivider and an output for providing a control signal representative ofthe position of the point actuation; a usage detection circuitoperatively coupled to the output of the touch sensitive device fordetermining if the point actuation is presently occurring; a stabilizingcircuit operatively coupled to the output of the touch sensitive deviceand comprising an output, the stabilizing circuit comprising awhacking-grade capacitor for stabilizing the control signal of the touchsensitive device, the capacitor operable to charge and discharge throughthe resistive divider of the touch sensitive device, such that thecontrol signal is representative of the position of the point actuation;and a controller coupled to the usage detection circuit and the outputof the stabilizing circuit, the controller operable to determine whenthe point actuation is presently occurring in response to the usagedetection circuit, the controller responsive to the control signal onlywhen the point actuation is presently occurring.
 34. The user interfaceof claim 33, wherein the capacitor and resisitive divider arecharacterized by a time constant, said time constant being in a range offrom about 0.006 second to about 0.015 second.
 35. The user interface ofclaim 34, wherein said time constant is about 0.013 second.
 36. The userinterface of claim 33, wherein said capacitor has a capacitance from 4to 10 microfarads.
 37. The user interface of claim 36, wherein saidcapacitor has a capacitance of about 9 microfarads.
 38. The userinterface of claim 33, wherein said touch sensitive device comprises athree-wire touch screen for producing an output related to the positionof the point actuation along the longitudinal axis of said touchsensitive front surface.
 39. The user interface of claim 33, whereinsaid touch sensitive device comprises a four-wire touch screen havingfirst and second electrodes at the top and bottom respectively of saidtouch sensitive device for producing a y output voltage related to theposition of the point actuation along the longitudinal axis of saidtouch sensitive front surface, and having third and fourth electrodes atrespective sides of said touch sensitive device for producing an xoutput voltage.
 40. A method of receiving a control signal from a touchsensitive device, the touch sensitive device comprising a resistiveelement and responsive to an operating pressure applied thereto, themethod comprising the steps of: generating a touch control signal inresponse to the operating pressure being applied to the touch sensitivedevice, the touch control signal representative of the position at whichthe operating pressure is applied to the touch sensitive device;filtering the touch control signal with a capacitor to generate afiltered control signal using a time constant ranging from approximately6 milliseconds to 15 milliseconds, wherein the capacitor is operable tocharge and discharge through the resistive element; monitoring the touchcontrol signal to determine if the position at which the operatingpressure is applied to the touch sensitive device is presently changing;and determining the position at which the operating pressure is appliedto the touch sensitive device from the filtered control signal inresponse to the step of monitoring.
 41. The method of claim 40, whereinthe step of monitoring further comprises the steps of: monitoring thetouch control signal for a predetermined number of brief intervalsduring a predetermined period of time; and determining that the positionat which the operating pressure is applied to the touch sensitive deviceis presently changing if the touch control signal is changing during thepredetermined number of brief intervals.
 42. The method of claim 40,wherein the step of filtering further comprises the steps of: samplingthe touch control signal to obtain a sampled value; rotating the sampledvalue into a buffer; repeating the steps of sampling and rotating apredetermined number of times; and averaging the sampled values of apredetermined range of the buffer.